I have one available. I used a Centra sight raising block, the result was that I had to do the screw up very tightly as the dovetail wasn't quite right. Eventually the allen fitting became impossible to undo, so it was drilled out. I was given a replacement foresight tunnel, but managed to get a new screw which fitted fine, so I now have a spare which you can have for about £5 which is what I guess the postage will cost.